Question

A plant extract can be obtained with organic solvents such as acetone or ethyl alcohol and is composed of plant pigments such as chlorophyll A and B carotene and xanthophylls.
Write a brief explanation about why a plant extract is a mixture, whether it is homogeneous or heterogeneous and how it can be separated.

Answer 1

Plant is complex biological organism which is composed of many organic molecules that fulfill different roles in the plant, some will give the color of the plant, some are "energy reactors" like chlorophyll which capture the photons for promoting certain chemical reactions. Now the organic solvents like acetone and ethyl alcohol do not discriminate between the compounds so the solvent will extract many different molecules from the plant. The extract will be definitely a heterogeneous one.

Using a thin lay chromatography plate you may determine the spots for each organic compound as well as their retention factor for the solvent used as eluent.  After concentration the solution, under vacuum, the mixture may be loaded in a chromatography column, previously filled with silica gel as stationary phase. After the elution and collection of each fraction, that contain a different molecule, the plant extract is separated.